The Fujita Scale allows for direct measurement of wind speeds and the EF scale does not. The EF scale is a "damage" scale only.

Here is an illustration of the latter point that the original F-Scale allows for direct measurements.

The Wichita Eagle has an article, published today, written by Stan Finger on the research being done to fix the EF-Scale. Given the information in the article, they are finding that Ted's original numbers (higher wind speeds) were much more accurate than those in the EF Scale. They expect to have a third scale in about 18 months.

Given the information in Stan's article, they might save themselves a lot of work and simply go back to Ted's original scale.